Next story in Space

The thick, hazy atmosphere of Titan, Saturn's largest natural satellite, hides a complex moon with a perplexing geological past, a new study finds.

Researchers from the Massachusetts Institute of Technology (MIT) in Cambridge and the University of Tennessee at Knoxville studied images of Titan to investigate the erosion of its terrain, over millions of years, by rivers of liquid methane.

The scientists found that in some regions, Titan's network of rivers caused surprisingly little erosion, which could indicate that erosion processes on Titan occur extremely slowly, or that a different, more recent phenomena is to blame for altering or eliminating ancient riverbeds and landforms, the researchers said.

Science editor Alan Boyle's blog: "Astronaut Abby" is at the controls of a social-media machine that is launching the 15-year-old from Minnesota to Kazakhstan this month for the liftoff of the International Space Station's next crew.

"It's a surface that should have eroded much more than what we're seeing, if the river networks have been active for a long time," study co-author Taylor Perron, an assistant professor at MIT, said in a statement. "It raises some very interesting questions about what has been happening on Titan in the last billion years."

Peering into Titan's past
Titan is estimated to be approximately four billion years old, roughly the same age as the rest of the solar system, the researchers explained. The moon's dense atmosphere, largely made up of methane and nitrogen, created a thick orange haze that prevented astronomers from being able to see through to the surface.

In 2004, however, NASA's Cassini spacecraft pierced through Titan's cloudy cloak and snapped the first set of detailed radar images of the moon's surface. Cassini occasionally flies past Titan as it orbits Saturn.

The images showed that Titan's icy terrain was carved out over millions of years by rivers of liquid methane, similar to how rivers on Earth leave their mark on the planet's rocky continents, the researchers said. But, while Titan's current landscape is now well documented, its geologic past remains a mystery. [Amazing Photos: Titan, Saturn's Largest Moon]

Most moons in the solar system are heavily pockmarked, with impact craters dotting their surfaces. Titan, on the other hand, is relatively smooth, despite the moon being roughly the same age as the rest of the solar system. Simply judging by its surface features, Titan would appear to be much younger, between 100 million and 1 billion years old, the researchers said.

To explain Titan's lack of craters, the researchers pointed to our own planet.

"We don't have many impact craters on Earth," Perron said. "People flock to them because they're so few, and one explanation is that Earth's continents are always eroding or being covered with sediment. That may be the case on Titan, too."

Finding clues on Earth
Geological processes, such as plate tectonics, erupting volcanoes, advancing glaciers and river networks, have altered Earth's surface over billions of years. According to the results of the new study, similar processes, including tectonic upheaval, icy lava eruptions, erosion and sedimentation by rivers, may also be factors on Saturn's largest moon.

Still, pinpointing which specific phenomena may have reshaped Titan's surface is a tricky task. Images taken by the Cassini spacecraft provide bird's-eye views of the terrain, with no details about a landform's elevation or depth.

"It's an interesting challenge," Perron said. "It's almost like we were thrown back a few centuries, before there were many topographic maps, and we only had maps showing where the rivers are."

To study how Titan's methane rivers eroded the moon's surface, the researchers mapped 52 prominent river networks from four regions. Images of these rivers were compared with a model developed by Perron of how a river network evolves over time.

Images of Titan were also compared with regions on Earth, including volcanic terrain on the island of Kauai and recently glaciated landscapes in North America. The researchers were able to draw parallels between our planet and Saturn's hazy moon, suggesting that similar geological processes may have altered Titan's icy surface in the recent past.

"It's a weirdly Earth-like place, even with this exotic combination of materials and temperatures," Perron said. "And so you can still say something definitive about the erosion. It's the same physics."

The detailed results of the study will be published in an upcoming issue of the Journal of Geophysical Research-Planets.

Southern stargazing

Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them.
(Y. Beletsky / ESO)
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A balloon's view

Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich.
(Kyle Moroney / AP)
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Spacemen at work

Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment.
(NASA)
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Special delivery

The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps.
(NASA)
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Accidental art

A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288.
(NASA / ESA)
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Supersonic test flight

A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

Red lagoon

The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes.
(ESO/VPHAS team)
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Fire on the mountain

This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people.
(NASA via AP)
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Where stars are born

An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues.
(NASA / JPL-Caltech)
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A long, long time ago...

This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang.
(NASA / NASA via AFP - Getty Images)
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Frosty halo

Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.